Polyphenylene ether resins are high performance engineering thermoplastics having relatively high melt viscosities and softening points (i.e., in excess of 200.degree. C.). They are useful for many commercial applications requiring high temperature resistance and can be formed into films, fibers and molded articles. However, the art has recognized that polyphenylene ethers have major drawbacks, and these are unattractive flow properties and a tendency to degrade by taking up oxygen at elevated temperatures. There have, therefore, been attempts to improve the flow properties and the oxidation resistance of these resins. Finholt, U.S. Pat. No. 3,379,792, for example, discloses the addition of a polyamide to the polyphenylene ether. The polyamides are formed from the condensation of diamines and dibasic acids and the self-condensation of amino acids as well as polyamides formed by the polymerization of lactams. Cizek, U.S. Pat. No. 3.383,435 discloses that improved processability of polyphenylene ether can be obtained by the addition of polystyrene and copolymers containing polystyrene including rubber modified high impact polystyrene. Butadiene containing additives are disclosed for the same purpose in Lauchlan, U.S. Pat. No. 3,660,531. More recently, Haaf et al., U.S. Pat. No. 4,563,500 disclosed adding a styrene resin and an impact modifying agent to polyphenylene ether to improve mold flow properties. The impact modifying agent comprises an elastomeric block copolymer of a vinyl aromatic compound and a conjugated diene and a hydrogenated derivative of the same. Holoch, U.S. Pat. No. 3,639,334, discloses that polyphenylene ether resins containing a small amount of a phosphite, a hydrazine or a mixture thereof show good resistance to embrittlement and discoloration at elevated temperatures in oxidizing atmospheres.
Despite these efforts, however, there is still an important need in the industry to improve the processability and the stability of polyphenylene ether resins.
It is therefore an object of the present invention to provide a polyphenylene ether resin composition with improved flow properties.
It is a further object of the invention to improve the oxidative stability of polyphenylene ether resins.
It is still another object to provide modified polyphenylene ether resin compositions with improved processability and thermal stability.